Television system



May 25 1937 H. H. BEVERAGE I 2,081,730

TELEVlS ION SYSTEM Filed March 22, 1932 Il I. a 65 5 yam/A703 79j/ HAROLD H. BEVERAGE ATTORNEY Patented May 25, 1937 UNTED STATES PATENT OFFICE TELEVISION SYSTEM Delaware Appiication March 22, 1932, Serial No. 600,411

17 Claims.

The present invention relates in general to television systems and is directed principally to a method and means for controlling automatically the modulation of the television transmitter which is being modulated by scanning either a subject in a studio or outdoor scene or by scanning a motion picture lm, with o1' without a sound accompaniment.

The invention herein will be described in connection with a general example and will be illustrated in this general form by making reference to a system used for scanning motion picture film. With television apparatus utilizing motion picture iilm as the source from which the intelligence transmission is to be taken it is known that the modulation level on the transmitter is continually changing. This change is due to the fact that the general overall density of different lm frames of the same motion picture lm is continuously changing as the film is advancedv relative to the transmitter scanner. If the modulation level on the transmitter is once set correctly for a film having a relatively light density the transmitter may be over-modulated when there is a sudden change from this light density lm to another nlm or another section of the same film of greater density. In this connection it is assumed that the modulation is produced by the darker portions of the film, although, of course, it is apparent that the system may be operated in the reverse manner.

It is also a general condition for satisfactory television transmission that synchronizing impulses should accompany the image signals and that the combined image synchronizing impulses should be transmitted, where possible, within a predetermined frequency band, i. e., in a single continuous communication channel. In order that the receiving points may be made responsive both to the synchronizing and the image signals in proper relationship it is necessary that the amplitude of the picture signals should at all times bear a denite relationship to the amplitude of the synchronizing impulses, otherwise the synchronizing apparatus at the receiving station, which is adjusted to be responsive only to the synchronizing impulses, would be affected by picture signals of abnormal value. This condition would cause the operating action of the receiving system to shift, or, in other words, it would disrupt the synchronism of the receiver. However, even in spite of this condition, wherein it is preferable to have the synchronizing impulses of an amplitude greater than the picture or image signals, it is nevertheless desirable to keep the amplitude of the picture signals as high as possible in order to maintain the highest efciency of transmission.

Therefore, in order to overcome the diliculties previously existing in systems known at present in the art, it is proposed in accordance with this invention to arrange the transmitter equipment in such manner that whenever changes in the average density occur in the film record, of which an electro-optical image response is to be produced at various points of reception, the changed density will serve automatically to control the modulation level of the transmitter.

A convenient form of arrangement by which these results may be accomplished has been shown by the accompanying drawing and consists briefly in ways and means to determine the average density of each particular frame portion of the motion picture film and to produce in accordance with the average density value of each particular film frame a signal of proportionate strength. Simultaneously with the production of the signal impulses or currents representative of the average density value of each nlm frame, the motion picture lm is scanned or analyzed in a series of elemental strips of which the varying intensity of light and shadow on each elemental area forming a part of each elemental strip produces a proportionately changing photo-electric current which is amplified in any suitable manner. In order that the degree of amplification may be controlled in accordance with the variations in density of each lm frame, the currents which are produced to represent the changing density values of each entire lm frame are applied in such manner that they serve as a means by which the picture or image signal amplified may be appropriately biased. One convenient form in which this apparatus may be arranged is to determine the average density value of each nlm frame of the complete motion picture lm at a time just prior to the time at which the lm frame is analyzed or scanned. Through the use of appropriate time delay circuits which function for each different produced signal representative of average film density to bias appropriately the picture or image signal amplier at the same time that the film frame previously tested as to density is being scanned, the modulation level can be adjusted. In this manner, it can be seen that by making a proper adjustment of volume setting of the television modulator at starting the amplitude of the resulting signals may be maintained continuously at the proper level irrespective of changes in the density of the film record being scanned for transmission.

From the foregoing it is apparent that one of the objects of the present invention is to provide for improved television transmission through the use of convenient means for automatically adjusting and maintaining the level of the picture voltage signals substantially constant and, at the same time, to maintain this level at such a value that the highest eiiiciency of transmission is maintained without permitting the picture or image signal to interfere with any signal indications by which synchronism is maintained at receiving points.

Another object of my invention is to provide ways and means whereby the varying changes in density on successive lm frames of a motion picture lm or the successive changes in the average value of light and shadow for direct pickup work may be made to cause a change in the level of response of an appropriate amplifier for amplifying the picture or image signals.

Other objects of the invention are to provide ways and means by which the modulation level of a television transmitter may be maintained constant and at a predetermined point with respect to the modulation produced by synchronizing signals used to accompany and, at the receiving points, to locate the points of reproduction of the electro-optical image effects used to represent the subjects located at the point of transmission.

Still other obj'ects of the invention are to provide ways and means by which the aforesaid results may be accomplished which are simple in their construction and arrangement of parts and, at the same time, will not involve any considerable amount of expense to install in present existing types of television transmission apparatus.

Still further objects of the invention will become apparent and at once suggest themselves to those skilled in the art to which the invention is directed by reading the following specification and claims in connection with the accompanying drawing, wherein the single figure thereof illustrates one form of the invention applied to the television transmission of motion picture lm record.

Now referring to the drawing accompanying this specification, it should be borne in mind that in the prior art, so far as I am aware, it has usually been customary to set manually the modulation level on the television transmitter by observing the output of the transmitter on a monitor screen. It is quite apparent that where the screen is not watched continuously and adjustments are not made for each change in density of the subject being scanned the transmitter is likely either to be under modulated or over modulated. Obviously, if the transmitter is under modulated, its service range is decreased and it does not produce clear pictures at the distant receivers. On the other hand, if the transmitter is over modulated, the images become blurred and, furthermore, in cases where the synchronizing impulses are sent on the same transmitter as the television modulation, the over modulation of the transmitter, as has been pointed out above, is very likely to change the intensity or shape of the synchronizing impulses to such a degree that the picture at the distant receivers falls out of synchronism. If this condition occurs, it is, of course, obvious that it will be disturbing to the observer and greatly detract from the entertainment value resulting from the transmission.

To overcome these di'cuities I have provided a transmitter equipment which may, for simplicitys sake, be considered as involving a means whereby a motion picture lm is moved at a uniform and continuous rate through a transmitter at which point it is scanned and synchronizing impulses are generated in accordance with the rate of scanning. Apparatus suitable for accomplishing these results has already been shown and described in connection with copending application of Joseph A. Briggs, Serial No. 587,005, led January 16, 1932, issued Oct. 6, 1936 as Patent No. 2,056,247.

To illustrate my present invention, a motion picture lm l i is arranged to be passed over lm feed rollers or sprockets i3 and l5 so as to be advanced continuously in the direction shown by the arrow. At a point il! a light source of constant intensity is arranged to direct its issuing light through an optical system i9 so as to illuminate an area equal to o-ne entire motion picture iilm frame. As the light from the source Il passes through an area equal to an entire motion picture lm frame it is directed through a diffusing screen 2i, which, for example, may be ground glass, and is arranged to fall upon a light responsive photo tube 23 supported jointly with the diffusing screen 2i in a housing 25. In accordance with the variations in intensity of light and shadow as produced by the average density of the lm Il causing currents to flow from the photo cell proportionate strength voltage drops appear across a resistor element 2l connected across the grid circuit of a vacuum tube amplifier 2Q and produce from the amplifier correspondingly varied output currents.

To analyze the varying intensities of light and shadow on each lm frame area, which intensities are to be utilized to produce the image or picture signals for transmission, a light source 3l of constant intensity is arranged to direct the issuing light through an optical system 33 so that the light passes through a series of concentrically arranged apertures 35 on a scanning element 37 which rotates about an axis 35 at constant speed. The light which passes through the apertures 35 of the scanning element is then directed by a lens ill, or the equivalent, so as to illuminate an elemental area of the motion picture film at a point 43. In accordance with the variations in intensity of light and shadow on this elemental area of the lm light passes to a second optical system and is then focused upon the cathode element of a light sensitive photo tube 4l. Variations in intensity of light falling on the cathode element of the photo tube il from the film record l l produce varying strength current in the photo tube circuit and produce varying voltage drops across a resistor 49. The Voltage drop produced in the resistor 49 connected to the grid or input electrode of the photo tube amplifier 5l, which couples the photo tube 41 with a picture signal amplifier 53, serves to produce a varying bias upon the tube and thus to control the current flow therefrom.

If now the amplification level of the amplier tube 5I is to be changed in accordance with the changes in average density of each lm area the currents which flow in the output circuit of the tube 29, the output current may then be arranged to charge, through a resistance 5l, a condenser which is connected in the input circuit of the amplier tube 5l. The time constant of the reincrease in the plate current output.

sistance 51 and the condenser 55 is adjusted to such a value that the gain of the picture signal amplifier tube 5| will be adjusted to a new value by the time the film which was explored for density reaches the point opposite the photo tube 41 where it is scanned or analyzed for image transmission purposes. Therefore, when the first frame of changed density is scannedopposite the density measuring photo tube 41 the picture signal amplifier 5| has already been set to the proper level for maintaining the correct modulation on the transmitter. Y

To describe now the operation of this device more fully, it may be stated that any description depends upon whether the modulation of the transmitter is to take place on the dark areas or on the light areas of the lm. The system herein disclosed, may be made to operate according to either of the above methods, but for the purpose of describing the operation it will herein be assumed that the modulation is produced by the dark portions of the film. In this case, the change-over switch 59 will be arranged so that it is thrown over on the left side contacts so as to connect the cathode of the photo tube 23 -with the cathode of the density signal ampliiier 29 and to connect the anode of the density measuring photo tube 23 with the gridor input electrode of this amplifier. However, if the modulation is to take place for the light areas of the film the position of the double-pole double-throw switch 59, used as a change-over switch, may be reversed to connect the anode and cathode of the photo tube oppositely with the same amplifier tube electrodes and the operation herein described will correspondingly be reversed.

Suppose now, for example, that the film being scanned at any particular instant is of relatively light density, this will mean that a considerable amount of light is able to reach the photo tubes 23 and 41. In this case, the photo tube 23, being supplied with a high light value, will cause the grid of the control amplier 29 to assume a negative potential, and thus the plate current flow from the tube 29 through the potentiometer 6| is relatively small and the IR drop through the potentiometer is also small. With this density film the grid of the amplifier tube 5| may be assumed to be operating with substantially normal biasing potential so as to permit the amplifier to operate at, or near, its full value. So arranged the current output from the picture analyzing photo tube 41 is amplied to a high degree, which is the proper condition, since there are assumed to be no over dark portions in the film for creating deep modulations.

Now suppose, for example, that a more dense subject on the film I arrives in front of the light source I1 so as to cause a decrease in the light falling upon the photo tube 23 used to determine average film density. The decrease in light upon the control photo tube 23 produced by the denser film section will cause the grid of the control tube 29 to become less negative and thereby cause an An increase in plate current output will increase the IR drop across the potentiometer 6|, suiiicient'to apply a negative potential on the capacity element 55 through the resistor 51 so that a negative charge is gradually built up upon the capacity element 55 to a value which is fixed by the amount of light falling upon the controlling photo tube 23. The resistance 51 and the capacity 55 are adjusted to such a value that this new potential reaches equilibrium by the time the film frame of changed density explored by the light source |1' can travel from a point opposite the control photo tube 23 to aposition for scanning opposite the scanning or analyzing photo tube 41. For example, if twenty-four picture frames per second are being scanned and the distance between the control photo tubef23 and to scanning photo tube 41 is equal to six picture frames, the time constant of the combination of resistance 51 and capacity 55 would be X24 or 1A of a second.

From this discussion, it will be noted that the denser film section has caused a negative potential to be placed upon the picture signal amplifying tube 5| to decrease the gain therefrom. When the dense film is scanned, the darker portions would tend to increase the modulation over that which was established for the less dense film section, but with the decrease in gain from the amplifier 5| automatic compensation for the change in density is provided.

The amount of control exerted by the control photo tube 23 may be varied by moving or adjusting the position of the slider element 63 on the potentiometer 6| forming a part of the control amplifier output circuit, and, similarly, the normal bias for the picture signal amplifier tube 5| may be varied or changed by varying the size of the battery 65 and the time constant on the variable bias means for the picture signal amplifier 5| may be changed by varying either resistance 51 or capacity 55, or both.

Instead of arranging the system to become reversible by changing the position of the changeover switch 59, as above suggested, it will, of course, be clear that this same condition may be obtainedby adding another stage of amplification in cascade with the control amplifier tube 29.

Wherev synchronizing signals are to be transmitted to accompany the produced image signals, as was suggested in the above mentioned disclosure of Joseph A. Briggs, a light source 61 is arranged to pass light through a series of apertures 69 upon the scanning element 31 so that after each elemental strip of the picture film frame has been scanned a light impulse will be supplied upon the synchronizing photo tube 1| which is connected with a synchronizing signal amplifier 13 and arranged to modulate, jointly with the resulting picture signals, the modulator 15. As was also disclosed in the above-mentioned Briggs application, after a complete motion picture film frame has been scanned a different type of synchronizing signal to indicate vertical synchronism may also be produced by varying the shaping of the last slot 69 on the scanning element 31, or, where necessary in order to reduce the size of the scanning element, a shutter disk rotating at reduced speed may be interposed between the light source 61 and the scanning element 31 so that the slot, to generate vertical synchronizing signals, may become eiiective only after a predetermined number of rotations of the scanning element.

For the purpose of transmission of the combined picture or image and synchronizing impulses, both of these signals are supplied to a modulator 15 which is connected in turn with an oscillator 11. The output of the modulator is then fed to an amplifier 19 from which point the energy is transmitted to various receiving points by way of an antenna system 8| or distributed over a `wire line network.

While the invention has herein been described as being applied to continuously moving motion picture lm records, it is nevertheless to be understood that it is equally well applied to systems utilizing an intermittent type of film record motion, and that the only important changes in structure necessary to produce this type of scanning are to substitute for the concentrically arranged apertures 35 on the scanning element 3l a series of apertures which are arranged according to a spiral formation, as was taught by Nipkow.

If recourse is had to intermittent types of lm scanning apparatus and, to accomplish this result, use is made of the usual spiral arrangement of the scanning apertures, it is usually desirable to arrange the system in such manner that the spiral path covers less than 360 degrees on the scanning disk where the disk is to make one complete rotation to scan each lm frame. With the apertures so arranged a blank space on the disk is provided between the end of the spiral series of apertures and the beginning of the same series. In the time required for the scanning element to rotate through this angle the lm may be stepped ahead to the next nlm frame to be scanned. A suitable arrangement by which this result may be accomplished has been shown and described in connection with an intermittent type of hlm projector for television transmission in Australian Patent #11,664 of 1928.

Furthermore, the invention is also applicable when utilizing intermittently moving lm to the omission of the second source of illumination used to determine density alone provided suitable ways and means for determining from the particular area being scanned at the instant the average density of the complete motion picture lm frame record. A suitable means to accomplish this result is to supply an auxiliary light bias upon the film and in accordance with this illumination determine the average film density. To compensate for the auxiliary light in photo tube 4"! the photo tube itself or its amplifier may be supplied with a compensating electric bias.

It should also be understood that the invention while herein described in connection with a rotary disk scanning element could likewise be accomplished through the use of similarly arranged drum scanners or mirror wheels, or the equivalent.

Also, it is to be understood that the scanning of the film record might, where desired, be aocomplished through the use of a cathode ray tube, such as has been suggested by British Patent #225,553, or by the pending application of V. K. Zworykin, Serial No. 448,834, filed May 1, 1930, assigned to Westinghouse Electric and Manufacturing Company.

The present invention also contemplates the desirability of transmitting a sound record related to the picture record simultaneously with the transmission of the electro-optical image signals. When the apparatus herein disclosed is used to transmit motion picture film on which there is an optical record in the form of a series of optical recordings produced at uniform spaced time intervals (usually 24 such recordings per second, assuming that the lm record is to be reproduced at a rate of feet per minute for a 35 milimetre film), this record is accompanied by a separate continuous audible record concomitant therewith. As was disclosed by an application of Fritz Schroter led on December 5, 1928, as Serial #323,837, or by U. S. Patent No. 1,810,188 granted June 16, 1931, to T. A. Smith, both the visual and the audible record may be simultaneously translated into signalling irnpulses and used to modulate simultaneously the transmitter. The modulation may, where desired, be in accordance with the showing in U. S. Patent #1,770,205 to Goldsmith & Weinberger, wherein the television image signals modulate a picture carrier frequency and wherein the picture carrier frequency is in turn modulated by a separate carrier removed therefrom by a predetermined frequency separation, and wherein the last named carrier is in turn modulated by the sound signals as appearing on the continuous record portion of the film.

One of the methods above suggested by which the sound signals may accompany the television signals is shown by the accompanying drawing wherein the picture lm record after passing over the spool or roller l5 passes over still an additional roller 33 and advances in the direction shown by the arrow. Light of constant intensity -f originating at a source 85 is directed through the optical system 87 so as to pass through the sound record portion 39 on the lm. The light passing beyond the film toward the optical system 9| is directed to a photocell 93 where the variations in l light cause correspondingly varied electrical signals. The photo cell 93 connects with the sound signal amplifier 95 whose output connects with a modulator S7. A carrier frequency suitable for the sound signal is generated by the oscillator 99 and is applied also to the modulator 91. The modulated carrier is then amplified by the amplifier ||l| and transmitted by the antenna |03 or carried by way of a transmission network or wire line to desired receiving points. form in which the sound transmission channel has been shown herein is intended to be purely schematic and, of course, represents only one of the many forms which can be utilized.

While the control feature has been shown as being applied to the first stage of amplification, it is equally obvious from the above description that this controlling action may be applied to a later stage in the amplification process where desired. Furthermore, while the invention has f herein been applied specifically to the scanning of a motion picture film record, it is to be understood that it is likewise applicabletoscanning conditions for studio or out door work, where the image impressed upon the ground glass area 2| will then be of substantially constant intensity for a long period of time but will control, in accordance with sudden changes in average density of the entire scene, the amplification level of the entire apparatus. In such an event, the

diffusing screen 2| may become unnecessary and the photo tube 23 alone may serve as the means which is sensitive to the average light value for the entire record or subject area being scanned.

Furthermore, while the invention for controlling the amplification level in this system in accordance with the average density of the lm sections or frames being transmitted has been described inv connection with three element vacuum tubes it is quite obvious that the same principles may be applied to systems wherein four element vacuum tubes commonly known as screen grid tubes, or other multi-electrode tubes may be used without departing from the spirit of the invention herein described.

In view of the above consideration, it is to be understood that the invention herein disclosed is to be considered in a broad sense and not limited to the particular form in which it has herein been disclosed. I, therefore, believe myself to be The entitled to make and use any and all modifications such as would suggest themselves fairly to those skilled in the art to Which the invention has been directed and such as would b ecome apparent to anyone versed in the same arts from a reading of the above specification in connection with the following claims, where I claim as my invention and desire to secure by Letters Patent the following: v

1. The method of controlling the modulation level in light responsive apparatus which comprises the steps of scanning a film record surface in a sequential series of transverse parallel adjacent strips; converting the changes in density.

of each elemental area thereof into proportional strength electric currents for producing modulation signals at levels subject to change; independently producing With a pre-established time separation from the record surface from which the first-named electric currents Were produced additional signals representing the average density of a complete frame area of the record, and controlling by the last named electric currents in accordance with each change in the signal strength thereof the produced level of modulation for the first named signals.

2. The method of producing electrical signals for television transmission from a lm record which comprises scanning the film record surface in a sequential series of transverse parallel adjacent strips, converting the changes in density of each elemental area thereof into proportional strength electric currents for producing modulation at levels normally subject to change, also producing with an established time period separation independent signals representing the average density of each complete lm frame of the scanned area of the film, and controlling in accordance with the intensity of the last named signals for each time period of change thereof the level of modulation produced by the image signals.

3. The method of operating television film transmitting apparatus Which comprises producing electrical currents which vary in intensity in proportion to the average density variations' above and below normal average density of the area to be scanned, producing with a predetermined time separation picture current signals for modulation from the same area to represent changes in the intensity of light and shadow on each elemental area of the entire scanned area, and controlling the intensity level of the picture current signals produced for modulation in accordance with the changes from average intensity by the first produced currents.

4. The method of operating lm transmitting apparatus which comprises producing electrical currents which vary in intensity in proportion to the average density variations above and below normal average density, subsequently producing electrical signals for modulation from the same film area to represent changes in the intensity of light and shadow on each elemental area of the lm frame, and controlling the intensity level of the signals produced for modulation in accordance with the changes from average intensity by the rst produced currents.

5. In television apparatus, the method of controlling the modulation level of signals Which comprises determining the average density of each television subject of which an image is to be transmitted, subsequently analyzing the variations inintensity of light and shadow of the corresponding elemental area of each television subject for transmission to produce therefrom image signals for modulation varying in accordance with the changes in intensity of light and shadow on the analyzed subject, amplifying the produced image signals, and controlling the amplification level of the image signals in accordance with changes above and below average density of each image representation so as to maintain substantially constant modulation levels.

6. In television apparatus, the method of controlling the modulation level of image signals which comprises determining the average density oi' each complete image representation to be transmitted, subsequently analyzing according to a predetermined pattern the variations in intensity of iight and shadow on each elemental area or the corresponding image representation for transmission to produce therefrom signals for modulation varying in intensity in accordance With the changes in intensity of light and shadow on the analyzed image representation, amplifying the produced image signals and controlling the amplification level of the image in accordance with changes above and below an average density value of each image representation to maintain the effect of substantially constant modulation levels.

7. In the art of transmitting television signals, the method which comprises producing image signals of intensities varying in proportion to the intensities of light and shadow upon each elemental area of an image subject of which an electro-optical representation is to be produced, producing at predetermined time periods during the production of the image signals a second series of normally constant strength signals for synchronizing at points of reception the location of electro-optical image points resulting from the image signals, amplifying both signals produced, producing a third signal representative of the average overall light value of each transmitted image subject, and controlling from the third produced signal the amplification level of the produced image signals to maintain a predetermined modulation ratio between the image and synchronizing signals.

8. In television film transmitting apparatus, means for determining the average density of each lm frame and producing therefrom signals of an intensity proportionate thereto, means for analyzing subsequently the corresponding film frame and producing therefrom electric currents of intensity varying in proportion to the variations in. intensity of light and shadow of each elemental area of each film frame, and means for controlling from the produced average density signals the effective intensity of each of the produced image signals.

9. In a television system, the method of transmission which comprises producing from a film subject image signals of intensities varying in proportion to the intensities of light and shadow upon each frame area of the film subject of which an electro-optical image representation is to be produced, producing at predetermined time periods during the production of the image signals a series of synchronizing signals for locating at points of reception the position of electro-optical image points resulting from the produced image signals, amplifying both signals produced, producing a third signal representation of the average overall light value of each transmitted image subject, and controlling from the third produced signal the amplication level of the produced image signals.

10. In a television system wherein the intelligence is transmitted from a continuous previously recorded image separated into a series of independent image representations, means for producing in accordance with the average optical density of each independent image representation a signal of an intensity proportional to the average density, means for subsequently and with predetermined time separation scanning in a series of elemental strips each divided into a plurality of elemental areas each image representation and producing therefrom electric image currents of intensities varying progressively in proportion to the variations in the intensity of light and shadow of each elemental area of each image representation, and means for controlling from the produced average density signal the effective intensity of the produced image signals for each complete image representation.

11. A television system comprising means for producing signals of an intensity varying in proportion to the average combined values of light and shadow of a subject of which an image is to be produced during a time period less than the period of persistence of vision, means for scanning the subject along predetermined paths during the same time period to produce therefrom a series of signals of an intensity progressively changing in proportion to the variations in intensity of light and shadow of each elemental area of the subject, means for producing at predetermined separated time intervals during the scanning period a series of normally constant intensity signals with a predetermined polarity separation from the image signals to be utilized at points of reception to locate the coordinate relationship of the produced electro-optical image signals, an amplifier for amplifying the produced image signals, and means for controlling the biasing potentials supplied to the amplifier in proportion to the variations in intensity of the produced density signals so as to vary the modulation level of the produced image signals and maintain a predetermined average relationship with respect to the synchronizing signals.

12. In a television apparatus for transmitting signals representative of a motion picture film record, means for producing signals of an intensity varying in proportion to the average density of each film frame of a motion picture film, means for scanning along predetermined parallel paths each lm frame of the motion picture film to produce therefrom image signals of intensity proportionate to the intensity of light and shadow of each elemental area of the film, means for producing at the end of each of the parallel paths of scanning a signal to be utilized at points of reception to control the position of reproduced image signals, means amplifying each of the produced signals, and means controlling the amplification level of the produced image signals in proportion to the variations in intensity of the produced density controlled signals.

13. In television film transmitting apparatus, means for producing signals of intensity varying in proportion to the average density of each film frame of the motion picture film, means for subsequently analyzing each film frame previously tested for average density and producing from the analyzing electro-optical image signals varying in intensity in accordance with the variations in intensity of light and shadow of each elemental area of the lm frame, means for amplifying the produced image signals, means for controlling the amplification level of the ampliiied image signals for each film frame in accordance with the changes in intensity of average density signals produced to represent each successive lm frame, means for producing constant intensity synchronizing signals at predetermined time intervals during the time of analyzing the intensity of light and shadow of each elemental area of each film frame, and means for modulating a transmitter by both said controlled level image signals and said synchronizing signals.

14. In television film transmitting apparatus, means for producing signals of an intensity Varying in proportion to the average density of each film frame of the motion picture film, means for scanning each lm frame previously tested for average density and producing from the scanning electro-optical image signals varying in intensity in accordance with the variations in intensity of light and shadow of each elemental area of the lm frame, means for amplifying the produced image signals, means for producing synchronizing signals of constant intensity at predetermined time intervals during the time of scanning each film frame, means for varying the ampliiication of the image signals in accordance with the strength of the film density signals to maintain a pre-established ratio between the ampliiied intensity of the image and synchronizing signals, and means for modulating a transmitter by both said controlled level image signals and said synchronizing signals.

15. In television apparatus for transmitting image and sound records appearing upon a motion picture nlm, means for producing for each iilm frame of the motion picture record a signal of an intensity varying in proportion to the average density of the lm frame, means for scanning each nlm frame previously tested for average density and producing from the scanning thereof a series of electro-optical image signals varying in intensity in accordance with the variations in intensity of light and shadow of each elemental area of the nlm frame, means for amplifying the produced image signals, means for producing line and frame synchronizing signals of constant intensity at a predetermined time interval during the period of scansion, means for independently producing signals representative of the sound record accompaniment on the film, means for varying the amplication level of the image signals only in accordance with the strength of the film density signals to maintain a pre-established ratio between the amplified signal strength of the image and synchronizing signals, and means for modulating a transmitter simultaneously by the controlled intensity image signals, the sound signals and the synchronizing signals.

16. In a telecinematographic transmitting apparatus, a film analyzer, means including said analyzer for producing a modulated current, a first electric current amplifier comprising electrical discharge tubes for amplifying said modulated current, a luminous source, means for directing across a film surface corresponding to a plurality of lines of analysis before said surface is analyzed light emitted by said source, a photoelectric cell responsive to the light directed across said film surface from said source, a circuit including a source of current and said photoelectric cell and an electrical discharge tube having at least an anode, a cathode and a control electrode, means for connecting the cathode and control electrode to said discharge tube to the electrodes of said photoelectric cell, a combination of resistance and capacity in the anode circuit of said discharge tube, means for applying to one electrode of said first discharge tube amplier a difference of potential between the terminals of the resistance whereby the variations in modulation due to variations in the mean transparence of the lm are diminished.

1'7. In a telecinematographic transmitting apparatus, a film analyzer, means including said analyzer for producing a modulated current, a first electric current amplier comprising electrical discharge tubes for amplifying said modulated current, a light source, a photoelectric cell, means for directing across a film surface corresponding to a plurality of lines of analysis before said surface is analyzed light from said source to said photoelectric cell, a circuit including a source of current and said photoelectric cell, an electrical discharge tube having at least an anode, a cathode and a control electrode, means for connecting said cathode and control electrode tc each of the terminals of the photoelectric cell. a resistance and capacity connected in the output circuit of said electrical discharge tube, and means for applying to one electrode of said first electrical discharge tube amplier the difference in potential between the terminals of the resistance, whereby the variations in modulation due to variations in the transparence of the film are diminished.

HAROLD H. BEVERAGE. 

